Automobile consumers are becoming increasingly demanding of automobile performance, including aesthetic/ergonomic performance. Of importance to the present invention is the aesthetic and ergonomic considerations of automobile noise, and more particularly, of the sound quality of the automobile noise spectrum in the passenger compartment of automobiles. Unduly annoying automobile noise, including, e.g., drive train noise, adversely influences the perceptions potential consumers have of the automobile. In contrast, a pleasant sounding automobile is desirable to many consumers.
Whether an automobile possesses pleasant sound quality only partly depends on the sound pressure level (i.e., the loudness) of the noise in the passenger compartment. The quality of the noise also bears importantly on whether the automobile will be positively or negatively perceived by a consumer. Not surprisingly, however, what constitutes good and bad sound quality is subjective, because the answer depends on human psychoacoustics. Nevertheless, as recognized by the present invention, the determination of the sound quality of an automobile must account for human psychoacoustics, because human consumers ultimately will be the judges of whether an automobile sounds agreeable or disagreeable.
To quantify automobile sound quality, efforts have been made to correlate automobile noise patterns with what test subjects regard as agreeable and disagreeable noise. Essentially, these efforts have required that human test subjects listen to automobile noises and then subjectively rank the various noises. The rankings are then statistically analyzed to rank particular sound characteristics on a scale of agreeability.
Unfortunately, the rankings tend to be somewhat ad hoc, derived, as they are, from a limited number of subjects and a limited number of recordings. Further, individual rating "systems" vary somewhat, person to person. Thus, such test results are not repeatable, in that one test can potentially indicate a sound characteristic to be relatively agreeable, and another test can potentially indicate the same sound characteristic to be relatively disagreeable.
Still further, methods that employ human test subjects are largely incapable of predicting the sound quality of proposed automobile designs, until a prototype of the proposed design can be built and its sound recorded and graded by human test subjects. Accordingly, as recognized by the present invention, it would be advantageous to determine the sound quality of the noise spectra of both existing and proposed automobiles based on the psychoacoustic agreeability of the noise spectra, without requiring the input of human test subjects.
It is therefore an object of the present invention to provide a method and apparatus for analyzing automobile sound quality which is objective and which does not require interactive human ranking of sound quality. Another object of the present invention is to provide a method and apparatus for analyzing automobile sound quality which accounts for human psychoacoustic judgement of sound. Still another object of the present invention is to provide a method and apparatus for analyzing automobile sound quality which is easy to use and cost-effective.